92 



III. PORPHYRIN CHEMISTRY 



oxidation had occurred on this methene group (Fig. 26, I). The absorption 

 spectra of the oxy porphyrin complex salts (hemochrome and copper com- 

 plex) bore close resemblance to those of the complex salts of phylloporphyrin, 

 which carries a methyl group on one of the methene groups (Fig. 25). The 

 free oxyporphyrin in ether was of blue-green color. Tts absorption spectrum 



Fig. 25. Phylloporph\Tin. 



(I, 650; II, 584; III, 546; IV, 511 m^l■, order of strength: I, IV, III, II) did 



not resemble that of phylloporphyrin, but rather that of Fischer's oxymeso- 

 porphyrin. Similarly its solution in 20% hydrochloric acid was not red, but 

 green, and had its strongest absorption band in the orange (I, 623.5; II, 

 568.5 m/i). The absorption spectra deviated more, however, from those of 

 Fischer's oxymesoporphyrin than could be due to the presence of vinyl 

 instead of ethyl side chains, and the oxyporphyrin had a much lower HCl 

 number (0.25). 



From these results it was concluded that in the complex salts the oxy- 

 porphyrin is present in the form of hydroxyporphyrin (formula I of Fig. 26) 

 with hydroxyl on one methene group, while the free porphyrin is tauto- 

 merized (perhaps only partially) to structure II (Fig. 26). These conclusions 



OH 



I II 



Fig. 26. a-Oxyporphyrin of Lemberg et al. {1698). 



were confirmed by Libowitzky and Fischer {1781,1732) by the isolation and 

 analysis of the corresponding copro compounds and by the benzoylation of 

 the hydroxyl group. In contradLstinction to the unesterified hydroxypor- 



